The present invention relates to a disk apparatus for recording and reproducing digital continuous data, such as video data. More particularly, the present invention relates to a disk apparatus capable of continuously reproducing digital data recorded in different positions with respect to the radius direction on a recording disk.
Video disks are being developed for recording and reproducing (writing and reading) digital video data in-and-from a storage medium, using digital video compression. One example of such a storage medium is an optical disk. The Moving Picture Experts Group (MPEG) is an example of one such digital video compression method.
In a conventional video disk apparatus using an optical disk, digital video data is temporarily stored in a buffer memory. Digital video data may he compressed by a digital video compressor, such as an MPEG encoder, or transmitted by broadcasting the data, or transmitting it via CATV (cable television). In the buffer memory, the difference between the bit rate (number of bits to be sent per second) of the input digital video data and the recording and reproducing speed (write-in and readout speed) of the optical disk (number of bits to be recorded/reproduced per second) is adjusted. In general, tile bit rate of the digital video data is slower than the bit rate of the recording and reproducing speed of the optical disk.
As an example of the application of such a video disk apparatus, a plurality of digital video data is recorded in different positions with respect to the radial direction of an optical disk and is reproduced in an optional order. For example, a digital video D1 starting from a radius R1 position, a digital video D3 at a radius R3 position, and a digital video D2 at a radius R2 position are to be reproduced in this order. Herein, R1 less than R2 less than R3. In this case, after reproducing the digital video starting from the radius R1, an optical head is moved to the radius R3 position so as to reproduce the digital video D3. Then, the optical head is moved to the radius R2 position for reproducing the digital video D2.
Since tile video data cannot be reproduced from the optical disk when the optical head accesses the optical disk, at the time of changing tie reproduction from the video D1 to tile video D3, or from the video D3 is to the video D2, the video is interrupted. That is, the videos cannot be reproduced continuously. In order to solve this problem, a technology has been proposed where two optical heads are provided in a laser disk apparatus, so that one is positioned at a radius position of a currently reproduced video, and the other one positioned at a radius position of a subsequently reproduced video. By switching the heads at the time of changing the videos, the reproduction incapability because of the access can be eliminated so as to enable the continuous video reproduction. However, this method has a major setback in that using two optical heads raises the cost.
An object of the present invention is to provide a video disk apparatus capable of continuously reproducing a plurality of digital continuous data, such as video data, stored in areas of different positions with respect to the radial direction of the recording medium, without interruption using one recording and reproducing head.
The present invention provides a disk apparatus comprising a continuous data input and output section for inputting and outputting continuous data at a first bit rate. The disk apparatus also comprises a recording and reproducing section for selectively recording and reproducing the continuous data in and from a disk-like recording medium at a second bit rate higher than the first bit rate. The disk apparatus further comprises a buffer memory coupled between the continuous data input and Output section and the recording and reproducing section. The buffer memory temporarily stores the continuous data to compensate the bit rate difference between the continuous data input and output section and the recording and reproduction section. Also, the disk apparatus comprises a control section. The control section controls the recording and reproducing section to successively reproduce, in a predetermined order, continuous data stored in a plurality of areas in the recording medium at different positions with respect to a radial direction of the recording medium. The control section controls the recording and reproducing section and the buffer memory. The buffer memory stores digital continuous data for a time length more then the access time for accessing the plurality of areas from the recording medium. The access is performed at a second bit rate in the data input and output section. The continuous data, stored in the buffer memory to the input and output section, is continuously read out during the reproduction operation and the access time of the recording and reproducing section.
According to the present invention, a plurality of digital continuous data, such as video data stored in areas in different positions with respect to the radial direction of the recording medium, can be reproduced continuously with one recording and reproducing head without interruption.
In a disk apparatus of tile present invention, digital continuous data, recorded in a recording medium, is reproduced at a speed higher than the bit rate of the digital continuous data for storage in a buffer memory, and the digital continuous data is read out from the buffer memory by the bit rate of the continuous digital data to reproduce the continuous video information.
Since the reproducing speed from the recording medium is higher than the bit rate of the digital continuous data, there is a speed difference between the speed for storing the digital continuous data in the buffer memory and the speed for reading the digital continuous data from the buffer rate. This results in digital continuous data accumulated in the buffer memory. When the capacity of the buffer memory becomes full, the reproduction from the recording medium is temporarily interrupted. During that period, the digital continuous data is read out at the bit rate from the buffer memory so as to reproduce continuous video information.
When the amount of digital continuous data recorded in the buffer memory is reduced to an appropriate value, the reproduction from the recording medium is resumed. Therefore, the digital continuous data is intermittently reproduced from the recording medium so that the digital continuous data is continuously read out from the buffer memory.
If the pause period of the reproduction from the recording medium is set at a period longer than the average access time of the recording and reproducing head, the recording and reproducing head can be moved. The head can be moved to an area at an optional different position with respect to the radial direction of the recording medium, thus utilizing the pause period to reproduce the other digital continuous data recorded in the area. During the access, the digital continuous data is read out from the buffer memory. Note that the digital continuous data was recorded in an area at the radial position of the recording medium where the recording and reproducing head was placed before moving. Subsequently, the digital continuous data is reproduced from the recording medium at the position where the recording and reproducing head is placed after moving, stored in the buffer memory, and read out from the buffer memory at the bit rate of the digital continuous data.
Accordingly, since the digital continuous data is read out and reproduced from the buffer memory even when the recording and reproducing head is moving, the digital continuous data recorded in areas of different positions with respect to the radius direction of the recording medium can be reproduced without interruption.
The memory capacity for a buffer memory in the present invention can be defined as A*S bits or more, where the bit rate of the digital continuous data is A (bps), and the maximum access time to the recording medium (seeking time for a recording and reproducing head to move from the innermost periphery of the recording medium to the outermost periphery plus time for the recording medium to make a rotation) is S seconds. By providing such a buffer memory, the amount of digital continuous data corresponding to the access time of the recording and reproducing head can be accumulated preliminary in the buffer memory, taking advantage of the difference between the reproducing speeds at which tile digital continuous data is reproduced from the recording medium, all the bit rate of the digital continuous data.
When re-seeking due to an unsuccessful seeking is performed, the memory capacity of the buffer memory can be set at A*S*(N+1) bits or more, where the bit rate of the digital continuous data is A (bps), and the number of the seeking retrials is N.
In a disk apparatus having a function for automatically replacing the recording medium, the memory capacity of the buffer memory can be set at A*S bits or more, where the sum of the maximum time for replacing the recording medium and the maximum access time to the recording medium (seeking time for a recording and reproducing head to move from the innermost periphery of the recording medium to the outermost periphery plus time for the recording medium to make a turn) is S seconds, and the bit rate of the digital continuous data is A (bps). Accordingly, since the digital continuous data for the replacement time of the medium and the access time to the medium can be stored preliminary in the buffer memory and the buffer memory can be read out during the time, a plurality of digital continuous data in areas of different optional positions with respect to the radial direction of a plurality of recording mediums can be reproduced without interruption.
When unsuccessful seeking and unsuccessful replacement of the recording medium occurs, and the seeking and replacing are retried, the memory capacity of the buffer memory can be set at A*S1 (N1+1)+A*S2*(N2+1) bits or more, where the maximum time for replacing the recording medium is S1 second, the number of the retrials at the time of an unsuccessful replacement of the recording medium is N1, the maximum access time to the recording medium (seeking time for a recording and reproducing head to move from the innermost periphery of the recording medium to the outermost periphery plus time for the recording medium to make a turn) is S2 seconds, the number of the retrials at the times of an unsuccessful seeking is N2, and the bit rate of the digital continuous data is A (bps).
Furthermore, in the present invention, when editing the digit continuous data, the editing efficiency can be improved by controlling the digital continuous data, which can be anticipated to be reproduced continuously before editing, since the editing operation can be confirmed before hand.
Addition al objects and advantages of the invention will be set forth in the description which follows, or may be learned by practice of the invention. The objects and advantages of the invention maybe realized and obtained by means of instrumentalities and combinations particularly pointed out in the appended claims.